Any difference between the sequence of bases within a gene in the individual genome being sequenced compared with and the sequence(s) held in the reference genome. If the mutation causes the gene or gene product to function differently or cease to function, this may cause disease. Some clinicians and patients prefer to use the term ‘variant’ as an alternative to ‘mutation’.
Use in clinical context
Depending on the context it can be more appropriate to refer to a mutation as a variant; the two terms can be used interchangeably. Often mutation is used to describe a variant that is known to be pathogenic or associated with a particular condition.